This invention relates generally to an inner compression member and an inner guide channel member for medical device delivery systems and, in particular, to a tapered inner compression member and a tapered inner guide channel member for medical device delivery systems that employ a catheter. These medical device delivery systems have a host of uses, including, for example, the deployment of a self-expanding implantable prosthesis at selected locations inside a patient's body. The invention may also be used, however, with a balloon expandable and non-expanding implantable prosthesis. In addition to being used with a rapid insertion delivery system, the invention may be used in an “over-the-wire” delivery system, so both systems will be described below.
By way of background, stents are configured to be implanted into body vessels having a passageway in order to reinforce, support, repair, or otherwise enhance the performance of the passageway. The term “passageway” is understood to be any lumen, channel, flow passage, duct, chamber, opening, bore, orifice, or cavity for the conveyance, regulation, flow, or movement of bodily fluids and/or gases of an animal. As an example, stents have been used in the passageways of an aorta, artery, bile duct, blood vessel, bronchiole, capillary, esophagus, fallopian tube, heart, intestine, trachea, ureter, urethra, vein, and other locations in a body (collectively, “vessel”) to name a few.
One type of stent is self-expanding. For a self-expanding stent, the stent is resiliently compressed into a collapsed first, smaller diameter, carried by the delivery system, and due to its construction and material properties, the stent expands to its second, larger diameter upon deployment. In its expanded configuration, the stent exhibits sufficient stiffness so that it will remain substantially expanded and exert a radially outward force in the vessel passageway on an interior surface of the vessel. One particularly useful self-expanding stent is the Z-stent, introduced by Cook Incorporated, due to its ease of manufacturing, high radial force, and self-expanding properties. Examples of the Z-stent are found in U.S. Pat. Nos. 4,580,568; 5,035,706; 5,282,824; 5,507,771; and 5,720,776, the disclosures of which are incorporated in their entirety. The Zilver stent, introduced by Cook Incorporated, is another particularly useful self-expanding stent due to its nitinol platform and use of the Z-stent design properties. Examples of the Zilver stent are found in U.S. Pat. Nos. 6,743,252 and 6,299,635, the disclosures of which are incorporated in their entirety.
Many delivery systems employ a tubular catheter, sheath, or other introducer (individually and collectively, “catheter”) having first and second ends and comprising a lumen for receiving the wire guide. Optionally, these delivery systems may fit through a working channel within an endoscope or an external accessory channel device used with an endoscope.
Generally stated, these delivery systems may fall within two categories. The first category of delivery systems to have been used, and consequently the first to be discussed below, is commonly referred to as an “over-the-wire” catheter system. The other category of delivery systems is sometimes referred to as a “rapid exchange” catheter system. In either system, a wire guide is used to position the delivery system within a vessel passageway. The typical wire guide has proximal and distal ends. A physician inserts the distal end into the vessel passageway, advances, and maneuvers the wire guide until the distal end reaches its desired position within the vessel passageway.
In the “over-the-wire” catheter delivery system, a physician places the catheter over the wire guide, with the wire guide being received into a lumen that extends substantially through the entire length of the catheter. In this over-the-wire type of delivery system, the wire guide may be back-loaded or front-loaded into the catheter. In front-loading an over-the-wire catheter delivery system, the physician inserts the distal end of the wire guide into the catheter's lumen at or near the catheter's proximal end. In back-loading an over-the-wire catheter delivery system, the physician inserts a distal portion of the catheter over the proximal end of the wire guide. The back-loading technique is more common when the physician has already placed the wire guide into the patient, which is typically the case today. In either case of back-loading or front-loading an over-the-wire catheter delivery system, the proximal and distal portions of the catheter will generally envelop the length of the wire guide that lies between the catheter first and second ends. While the wire guide is held stationary, the physician may maneuver the catheter through the vessel passageway to a target site at which the physician is performing or intends to perform a treatment, diagnostic, or other medical procedure.
Unlike the over-the-wire system where the wire guide lies within the catheter lumen and extends substantially the entire length of the catheter, in a novel “rapid insertion” catheter delivery system described in application Ser. No. 60/673,199, the wire guide occupies a catheter lumen extending only through a distal segment of the catheter. The so-called rapid insertion system comprises a system proximal end, an elongate flexible middle section and a system distal end that is generally tubular.
The system distal end, in general, comprises an inner guide channel member sized to fit within an outer guide channel member that is substantially axially slideable relative to the inner guide channel member. The outer guide channel member and inner guide channel member further have entry and exit ports defining channels configured to receive a wire guide. A port includes any structure that functions as an entry or exit aperture, cutout, gap, hole, opening, orifice, passage, passageway, port, or portal, while a guide channel is understood to be any aperture, bore, cavity, chamber, channel, duct, flow passage, lumen, opening, orifice, or passageway that facilitates the conveyance, evacuation, flow, movement, passage, regulation, or ventilation of fluids, gases, or a diagnostic, monitoring, scope, other instrument, or more particularly a catheter or wire guide.
A wire guide may extend from the outer and inner member entry ports, through the outer and inner member guide channels, and exit the distal end at or near a breech position opening located at or near a transition region where the guide channels and exit ports are approximately aligned relatively coaxially to facilitate a smooth transition of the wire guide. Furthermore, the outer guide channel member has a slightly stepped profile, whereby the outer guide channel member comprises a first outer diameter and a second smaller outer diameter proximal to the first outer diameter and located at or near the transition region.
The system distal end also has a self-expanding deployment device mounting region (e.g., a stent mounting region) positioned intermediate the inner guide channel member entry and exit ports for releasably securing a stent. At the stent mounting region, a stent is releasably positioned axially intermediate distal and proximal restraint markers and sandwiched transversely (i.e., compressed) between the outside surface of the inner guide channel member and the inside surface of an outer guide channel member.
Turning to the system proximal end of the rapid insertion delivery system, the proximal end, in general, comprises a handle portion. The handle portion has a handle that the physician grips and a pusher stylet that passes through the handle. The pusher stylet is in communication with—directly or indirectly through intervening parts—the inner guide channel member at the distal end. Meanwhile, the handle is in communication with—directly or indirectly through intervening parts—the outer guide channel member at the distal end. Holding the pusher stylet relatively stationary (while, for example, actuating the handle) keeps the stent mounting region of the inner guide channel member properly positioned at the desired deployment site. At the same time, proximally retracting the handle results in a corresponding proximal movement of the outer guide channel member relative to the inner guide channel member to thereby expose and, ultimately, deploy the self-expanding stent from the stent mounting region. At times, a physician may need to deploy a second self-expanding stent by withdrawing the system from the proximal end of the wire guide. The physician may then reload the catheter with additional stents, and if that is not an option the physician may load another stent delivery system with an additional stent, onto the wire guide. Also, the physician may withdraw the stent delivery system altogether and replace the delivery system with a catheter or different medical device intended to be loaded onto the wire guide.
The delivery system in the rapid insertion delivery system further comprises an elongate flexible middle section delivery device extending intermediate the system proximal end and the system distal end. The middle section delivery device comprises an outer sheath and an inner compression member having first and second ends associated with the system distal end and system proximal end, respectively.
More particularly, the outer sheath first end may be coterminous with or, if separate from, may be associated with (e.g., joined or connected directly or indirectly) the distal end outer guide channel member at or near the transition region, while the outer sheath second end is associated with the handle at the system proximal end. The inner compression member first end is associated with the distal end inner guide channel member at or near the transition region, while the inner compression member second end is associated with the pusher stylet at the proximal end. Therefore, the outer guide channel member of the distal end may move axially (as described above) and independently relative to an approximately stationary inner guide channel member of the system distal end and, thereby, deploy the stent.
Before the novel “rapid exchange” catheter delivery system described in application Ser. No. 60/673,199 and the present invention, the ways of associating the inner compression member first end to the inner guide channel member has typically been to use a mechanical lap joint. A lap joint, however, may increase the manufacturing time because it introduces a third part for joining the inner compression member and inner member. Also, the small physical dimensions of the lap joint, inner guide channel member, and inner compression member first end all are factors that increase the difficulty in manufacturability and, therefore, the assembly time. Another drawback to a mechanical lap joint connection is the propensity to lose the friction fit between the components. Accordingly, a glued joint is often employed as an alternative to a mechanical lap joint. While glue, adhesives, and the like (collectively, “glue”), offer advantages over a mechanical lap joint, one must choose the right glue to join dissimilar materials. Also, glue must cure, thereby increasing the total processing (fixture) time in the application and assembly of the joint. In any event, lap joints and glued joints may vary in strength and integrity depending on the type of materials being joined, and whether the materials have incongruous mating surfaces. In addition, the point attachments that are typically formed by these joints could cause joint failure due to inadequate stress distribution. Moreover, lap joints and glued joints tend to have point attachments that have non-uniform or irregular flexibility relative to the remainder of the joint or the region of the inner compression member or inner guide channel member held by the joint. As the device negotiates a tortuous path within a vessel passageway and “pushes” the inner guide channel member during stent deployment, the forces encountered by the distal end of the device may result in prolapse, buckling, kinking, or an irregular bend at or near the joint.
It would be desirable to have relatively uniform flexibility through the joint. Therefore, the present invention solves these and other problems by providing an inner compression member having a tapered portion. In another aspect of the invention, the inner compression member distal mating end comprises a second portion with an even smaller cross sectional area. In yet another aspect of the invention, a joint operatively couples the tapered portion and/or the second portion of the distal mating end of the inner compression member to the inner guide channel member.
Before the novel “rapid exchange” catheter delivery system described in application Ser. No. 60/673,199, another problem often encountered with conventional inner guide channel members is that the wall has uniform thickness and/or sudden changes in dimensions. The uniform dimension is less compliant (e.g., less flexible) compared to walls that get progressively thinner and, therefore, more compliant (e.g., more flexible). Also, sudden changes in a wall dimension could result in kinking or buckling of the wall at the point where the wall suddenly changes its dimension from, for example, thicker walls to thinner walls. Moreover, an inner guide channel member that has a uniform thickness will effectively require more space within the device, because the stent still needs to disposes about an outer diameter of the inner member.
Therefore, it would be desirable to have tapered inner compression member and a tapered inner guide channel member for a medical device delivery system such as, for example, a delivery system for self-expanding devices such as stents, prosthetic valve devices, and other implantable articles inside a patient's body as taught herein.